Banerjea, R.Y., Bell, M.G., Matthews, W and Brown, A.D. (2015) Applications of micromorphology to...

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Archaeological and AnthropologicalSciences ISSN 1866-9557Volume 7Number 1 Archaeol Anthropol Sci (2015) 7:89-112DOI 10.1007/s12520-013-0160-5

Applications of micromorphology tounderstanding activity areas and siteformation processes in experimental hutfloors

Rowena Y. Banerjea, Martin Bell, WendyMatthews & Alex Brown

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ORIGINAL PAPER

Applications of micromorphology to understanding activityareas and site formation processes in experimental hut floors

Rowena Y. Banerjea & Martin Bell & Wendy Matthews &Alex Brown

Received: 20 February 2013 /Accepted: 1 October 2013 /Published online: 6 December 2013# Springer-Verlag Berlin Heidelberg 2013

Abstract Experimental buildings at Butser Ancient Farm andSt. Fagans (UK) and Lejre (Denmark) were sampled toinvestigate micromorphology of known activity areas, tocontribute to our understanding of the internal use of spacein excavated buildings and formation processes of house floordeposits. The experimental buildings provided importantinformation relating to activity residues and sediments overthe 16 years that the buildings were in use. Specifically, theseresults contribute to our understanding of the routes and cyclesfor transportation of materials in occupation contexts, whichcan be used to inform archaeological studies. It has beenpossible to identify internal ‘hot spots’ within the buildingsfor the deposition of activity residues and for the formation ofspecific deposit types. Analysis also highlighted post-depositional alterations occurring in internal occupationdeposits, which has provided a means of identifying roofedand unroofed spaces in the archaeological record.

Keywords Experimental archaeology . Geoarchaeology .

Micromorphology . Formation processes

Introduction

A key issue that confronts archaeologists working onsettlements concerns the identification and interpretation of

activity areas, and particularly the ability to identify stages inthe life history of buildings (La Motta and Schiffer 1999) andthe associated occupation deposits. In order to address this,archaeologists must understand the pre-depositionalenvironment, the formation of archaeological deposits andthe post-depositional processes that effect archaeologicalstrata. Understanding these formation processes is central tointerpreting the archaeological record (La Motta and Schiffer1999; Schiffer 1987). Anthropogenic sediments withinsettlements have complex depositional and post-depositionalformation processes, which provide challenges forgeoarchaeologists in interpreting the origin of activity residuescontained within them. Consequently, micromorphology hasbecome an important tool in reconstructing the use of spaceand in interpreting formation processes within archaeologicalbuildings (Matthews 1997).

Experimental archaeology can play an important role inadvancing such interpretations through creating a database ofreference material from known activity areas and internalspaces, which can be used to provide more robustinterpretations of the archaeological record. In this experimentalresearch, buildings reconstructed from archaeological site plansat Butser Ancient Farm (Hants., UK), Lejre Historical andArchaeological Research Centre (Denmark), and St. Fagans,(National History Museum Cardiff, Wales) were subject tosmall-scale excavation and thin section micromorphologysampling to investigate the formation of the sedimentary record,in order to provide these comparative reference data. Most ofthe buildings investigated were constructed 16 years prior tosampling and have housed a range of activity spaces over theirlifetime. These sites enable formation processes withinbuildings to be studied in a temperate climate in differentgeological settings, providing examples which will informinvestigation and interpretation of activity traces in a range ofsettlement archaeological contexts, on a range of substrates.

These experimental archaeological contexts enabledtargeted examination of known activity areas, specific

Electronic supplementary material The online version of this article(doi:10.1007/s12520-013-0160-5) contains supplementary material,which is available to authorized users.

R. Y. Banerjea (*)Quaternary Scientific, School of Human and EnvironmentalSciences, University of Reading, Reading, Berkshire, UKe-mail: [email protected]

M. Bell :W. Matthews :A. BrownDepartment of Archaeology, School of Human and EnvironmentalSciences, University of Reading, Reading, Berkshire, UK

Archaeol Anthropol Sci (2015) 7:89–112DOI 10.1007/s12520-013-0160-5

Author's personal copy

http://dx.doi.org/10.1007/s12520-013-0160-5

depositional processes and taphonomy within structures at themicrostratigraphic scale, at a high chronological resolution.Specific processes such as dumping, trampling, decay andcollapse were readily observed in the experimental buildings.The data from the experimental structures provide moderncontextual analogues for archaeological research,supplementing data acquired from ethnoarchaeologicalresearch (Matthews et al. 2000; Milek 2012; Villagran et al.2011) and previous experimental research (Canti et al. 2006;Macphail et al. 2004; Macphail et al. 2006; Rasmussen 2007).

Examining the formation of occupation depositswithin structures

In many archaeological sites, few artefacts were left on thefloors where they were used, and many end up in rubbish pitsor middens, or were recycled (Nicholas and Kramer 2001).These artefact biographies have been documentedethnographically (Kent 1984; Kramer 1982; Schiffer 1987).Larger artefacts and bioarchaeological remains are oftenremoved from primary accumulation contexts, either bysweeping (La Motta and Schiffer 1999; Metcalfe and Heath1990; Schiffer 1987), or by levelling activities duringrefurbishment (Carver 1987). Within a building, refuse thathas accumulated on the floor during primary deposition tendsto consist of objects small enough to escape cleaning.Therefore, in regularly maintained areas, primary refuse willmore than likely be small artefacts, as stressed by theMcKellar principle (Schiffer 1987), or micro-refuse (LaMotta and Schiffer 1999; Metcalfe and Heath 1990; Schiffer1987).

Previous research has highlighted a series of issues toaddress when reconstructing archaeological site-formationprocesses and thereby settlement spaces and their associatedactivity residues. For example, the importance ofunderstanding the transportation mechanisms and pathwaysof plant remains (Greig 1982, p. 64;Matthews 2010), mineralsand micro-artefacts (Schiffer 1987, p. 14; Rosen 1993) intooccupation contexts, including processes such as transport bywind and introduction by trampling (Gé et al. 1993), has beenshown. These processes can affect the identification of in situactivity areas. In addition, the taphonomy of plant microfossilassemblages in occupation contexts, such as the factorsinfluencing the production and distribution of pollen andphytoliths (Tsartsidou et al. 2007; Tsartsidou et al. 2008) andtheir sources and catchments (Greig 1982, p. 64; Harvey andFuller 2005; Macphail 1981; Shahack-Gross 2011) must beconsidered when interpreting assemblages. The differentialpreservation of biological materials also affects theinterpretation of assemblages within the archaeological record(Boardman and Jones 1990; Robinson 2006; Shillito andAlmond 2010; Stevens 2003; van der Veen 2007). Post-depositional processes such as bioturbation and decay can

alter sediment/soil chemistry (Brady and Weil 2002;Breuning-Madsen et al. 2003; Canti 1999; Entwistle et al.2000; Kabata-Pendias 2001) and rework stratigraphy andactivity residues (Canti 2003; Canti 2007; Macphail 1994).

Micromorphology enables investigation of the use ofsettlement space through identification of depositionalpathways, through the study of micro-residues in situ withintheir sedimentary matrix and evaluation of their depositionaland post-depositional histories (Jones et al. 2010; Matthews1995; Matthews 2000; Matthews and Postgate 1994;Matthews et al. 1997; Macphail et al. 2004; Milek 2005, pp.98–104; Milek and French 2007; Shahack-Gross et al. 2005;Simpson et al. 2006; Sveinbjarnardóttir et al. 2007), as well aschemical alterations to archaeological stratigraphy (Canti1999; Canti 2003; Canti 2007; Courty et al. 1989).

By using micromorphology to investigate modernoccupation deposits in experimental buildings, this researchaims to provide diagnostic sediment attributes to identifyspecific transportation mechanisms of materials within thearchaeological record.

Investigating the spatial distribution of processesand activities in structures

This experimental research has also enabled horizontalsampling and spatial analysis of the composition, origin anddeposition of activity residues in relation to the known activityareas. A range of agencies and processes can affect the use ofspace within a building and the final interpretation ofarchaeological artefact and biological assemblages. It isrecognised that social and cultural considerations, agenciesand contexts affect the selection, placement, deposition andpost-depositional alterations of architectural materials andactivity residues (Sillar and Tite 2000; Robb 2010; Boivin2000; Matthews 2005). By using micromorphology onexperimental contexts, this research will investigate theinfluence of the building superstructure such as uprightsupports and the location of doorways, structuralmodifications and the influence that the layout of internalfurniture has on deposit type formation and deposit survivalwithin buildings, in order to develop previous researchconcerning the production, placement and decay ofconstruction materials (Goldberg and Macphail 2006;Matthews 1995).

Materials and methods

Experimental archaeology sites and sampling strategy

At Butser, the Longbridge Deverill Cowdown roundhousereconstruction, built in 1992, was excavated under rescueconditions in December 2006 because the building was

90 Archaeol Anthropol Sci (2015) 7:89–112


collapsing and replacement was imminent (Bell 2009).Consequently, the building and its deposits are not recordedin as much detail as those subsequently investigated. For theother buildings, a robust field methodology was developed torecord sediments and processes in detail, and included detailsof construction materials, structural modifications, primaryactivities, impact activities, hearth usage, operational chains(‘chaîne opératoire’), intensity of use, vegetation and geologyin the immediate vicinity, and wildlife infestations within thebuildings (see Banerjea 2011 for full descriptions). Thebuildings from Lejre were sampled in August 2007 andrecorded in more detail, as was the metalworking shed atButser, sampled in December 2007. At St. Fagans, thecollapsing Moel-y-Gaer roundhouse was excavated andrecorded in detail by Professor Martin Bell and a team fromUniversity of Reading in 2009. Fieldwork at Butser, Lejre andSt. Fagans experimental sites enabled sediment recordingmethods to be compared (Banerjea 2011), and presented anopportunity to collect samples from a range of occupationcontexts and activity areas from buildings with differentunderlying substrates. A summary of the activities andprocesses that were targeted for sampling in each building isgiven in Table 1.

Geology and soils of the study areas

Butser Ancient Farm, Hants, UK (Fig. 1), lies on UpperCretaceous Chalk overlaid by a thin patchy drift of solifluctedclay-with-flints, a sandy clay loam with gravel-sized flintinclusions on which a silty Ap plough rendzina with slightlyalkaline pH 7.3–7.8 developed. Soils on the slope showevidence of past decalcification during stable episodes,cultivation increased chalk content and led to erosion events(Bell 1983). Construction of the experimental site followed anarable phase. The Lejre Historical and ArchaeologicalResearch Centre, near Roskilde, Denmark (Fig. 1) lies onWeichselian glacial till, the soil is an Alfisol, silty with sandand few stones an acidic pH 5.5, and a tendency to ironmobilisation (Breuning-Madsen et al. 2001). The glacial tillsediment profile was recorded in a clay pit profile adjacent toBuilding 2. St. Fagans National History Museum, nearCardiff, Wales (Fig. 1) lies on Devensian glacial till with anacidic brown earth soil of the Radyar Series and ph 4.6–5.7.

Longbridge Deverill Cowdown Roundhouse, Butser

At Butser, most of the storm-damaged roof had been removedapproximately 1 month before sampling, leaving only part ofthe west side of the roof giving partial protection to theremains of the floor on the west side of the building, providingan opportunity to compare a recently unroofed space with theoriginal roofed space (Figs. 2 and 3). The northern half of theroundhouse was selected for sampling (Fig. 2) as this provided

the widest range of activities, materials and formationprocesses to be recorded and analysed (Table 1). The westhalf included the hearth, intact eaves and areas of bothundisturbed and disturbed non-constructed floor surfaces(for definition see Table 2). The previous activities withinthe Longbridge Deverill Cowdown experimental roundhousewere mostly recalled from memory by the staff at ButserAncient Farm. Two samples were collected covering storagelocations of thatch, food preparation including some minorcereal processing, food cooking, lead working and bronzefinishing (Table 1). In addition, daub and plaster that haderoded and fallen around the edges of the walls, was alsosampled to characterise construction materials. SampleBLD1 was collected from the centre of the hearth to studyfuel, concentrations of remaining hearth activity residues andheat effects on sediment. This had been exposed for 2 weeksprior to sampling as the roof was demolished. Sample BLD3was collected from the semi-unroofed floor area to study post-depositional weathering effects and trampling. These areshown on Fig. 3.

Metalworking workshop, Butser

The metalworking workshop at Butser was a three-sidedstructure with an open frontage, and as a result, the area andinternal deposits were exposed to weathering and erosion. Thefloor was a non-constructed/prepared surface that had formedthrough trampling of the Ap horizon. One sample, B14, wascollected from the trampled silty clay loam Ap horizon(context 003) in the area of the doorway where ore crushingand bronze casting and moulding activities took place(Table 1).

Building 2, Lejre

Since 1974, Building 2 (Fig. 4, Table 1) had been inhabited byfamilies recreating an ‘Iron Age life-style’, but only during thesummer months and Danish Autumn school holiday. As aresult the hearth, grindstone and fuel containers have beenused, creating different activity areas within the building. Thestable area of Building 2 housed animals between 1965 andthe early 1980s and since then has been used as a storeroomfor agricultural tools (Table 1). The entrance area houses havetwo fuel boxes located on the right side of both entrances and agrindstone on the left when exiting out of the northern door. Inthe living room, there are beds/benches on either side of thecentral hearth; limited cooking had taken place on the hearth.The modifications to Building 2 provided opportunities totarget accumulations of residues for sampling. For example,the depressions caused by moving the upright posts in 1994enabled both grinding residues and sweepings to accumulate,and the axial dung channel provided a section through thestable floor. Samples were collected from each activity context

Archaeol Anthropol Sci (2015) 7:89–112 91


Tab

le1

Activities

andform

ationprocessesthatweresampled

with

ineach

build

ing

Site

Butser

Lejre

Building

LongbridgeDeverill

Cow

downRoundhouse

Metalworking

shed

Building2

Forge

Sample

BLD1

BLD3

B14

L1

L9

L15

L39

Location

Hearth/recently

exposedspace

Under

eaves/semi-

unroofed

space

Doorw

ay/unroofed

space

Stable

Fuelb

asket/

post-depression

Grindingstone/

post-depression

Metalworking

area

near

hearth

Activities

Foodcooking

Thatchstorage

Ore

crushing

Herbivore

penning

Maintenance

Cropprocessing

Iron

working

Leadworking

Minim

alcereal

processing

Bronzecasting

Operatio

nalchains

Operatio

nalchains

Operatio

nalchains

Food

storage

Bronzeworking

Bronzemoulding

Stuctural

modification

Structural

modification

Storageof

craft

materials

Formation

processes

Trampling

Trampling

Trampling

Trampling

Trampling

Trampling

Trampling

Weathering

Weathering

Weathering

Abrasion/erosion

Abrasion/erosion

Abrasion/erosion

Semi-abandonm

ent

Burning

Sem

i-abandonm

ent

Site

Lejre

St.F

agans

Building

Sunken-shack

Moel-y-Gaer

Sam

ple

L45

L51

SF6

3SF6

8SF71

SFWalledge

Location

Doorw

ay/roofedspace

Unroofedspace

Hearth/roofed

Hearth/roofed

Doorw

ay/roofedspace

Baseof

wall/roofedspace

Activities

Herbivore

penning

Herbivore

penning

Food

cooking

Food

cooking

Maintenance

Boneworking

Boneworking

Metalworking

Metalworking

Formation

processes

Trampling

Trampling

Burning

Burning

Trampling

Collapse

Abandonment

Abandonment

Abrasion/erosion

Weathering

Seconadryuse

Seconadry

use

Collapse

Soildevelopm

ent



within Building 2 (Fig. 4; Table 1): sample L1 from the stable(context 001); L9 from the sweeping residues adjacent to thefuel basket (context 004) which included the earthen floorsurface (context 005); and L15 from grinding residues thataccumulated in the upright post-depression (context 006) alsoincluding the earthen floor surface (context 005).

Forge, Lejre

The reconstructed forge in the Iron Age Village (Fig. 4) hadbeen used for iron smithing activities between 1978 and 2002.Between 2003 and 2005, the central room was used to storecraft materials for weaving and pottery activities and potscontaining supplies of barley, wheat and horse beans. Since2006, the building has been semi-abandoned, only utilised as astaff shelter (Table 1). At the time of sampling, the buildingserved as a ‘display forge’ for visitors. One micromorphologysample, L39, was collected from the disused forge and was

strategically selected from an area which maximised theinclusion of activity residues, at equal distance from the hearthand anvil to include both ashes and hammerscale. L39comprised the residues on the surface and the non-constructed earthen floor (contexts 013 and 014 respectively).Analysis of sample L39 also enables the trampling effects on anon-constructed earthen floor surface to be studied (Table 1).

Sunken-shack, Lejre

Thewalls of the sunken-shack (Fig. 5) in theViking villagewereassembled using a plank constructionwith rocks and turf stackedagainst the external sides. There was no internal rendering andthe planks were untreated. The roof was also assembled using aplank construction; however, planks were missing due to decayand animal damage from area B (Fig. 5) despite repair in 2000.Area A (Fig. 5) remained partially turfed and water-proofedusing tar paper (a glass fibre or polyester fleece impregnated

Fig. 1 Map showing the locationof the experimental sites (ButserAncient Farm, Lejre Historicaland Archaeological ResearchCentre, St. Fagans,NationalHistory Museum,Wales)

Fig. 2 Sampling area (A) andexcavation sketch-plan (B) in thenorthern half of the LongbridgeDeverill Cowdown roundhouse,Buster Ancient Farm. Thefollowing activities wererecorded: storage of hay, timber,heather and reed matting underthe eaves; lead-working andcooking (stews and meat) on thehearth; bronze-finishing, cerealprocessing, cheese-making, foodpreparation and spinning wool inthe porch area



with bituminous material) during August 2007 when thefieldwork was undertaken. Tar paper was used for waterproofing when the use of the shack changed to house schoolchildren for activity demonstrations. The sunken-floor wascreated by digging a pit into the natural deposit of glacial till.Large granite cobbles were laid down as a floor surface onwhich occupation debris accumulated. The following activitycontexts and stages in the life history of the building werestudied: an occupation deposit, secondary use of space,abandonment and building collapse (Table 1). The changinguse of space within the sunken-shack is relatively well-documented in comparison with the other experimentalbuildings featured in this research. The sunken-shack wasoriginally used for bone working during school visits during1989–1996 (twice a week for a 10-week period each year). Thenthe sunken-shackwas utilised as a summertime livestock shelter,firstly for goats (1996–2006) and then for sheep (2006–2007).Sweeping and both human and animal trampling were alsodocumented for this structure. Previously undocumented,trampling and post-depositional soil development were recordedduring the fieldwork as additional formation processes that hadoccurred prior to the fieldwork (contexts 016 and 017,respectively). Each of these processes is provisionally thought

to be responsible for observed sedimentary differences betweenthe two contexts. The clear differences between contexts 016and 017 (Fig. 5) provided an opportunity to take comparativesamples from sediment apparently deposited during the sameevents but which has undergone different post-depositionalprocesses (trampling and soil development): micromorphologysamples L45 (016) and L50 (017).

Moel-y-Gaer roundhouse, St. Fagans

The Moel-y-Gaer roundhouse (Fig. 6) was constructed by DrP.J. Reynolds in 1992 using a circle of upright wooden poststhat held up a thatched roof. Inside, the wattle and daub wallswere coated with lime plaster. Four micromorphologysamples were collected during the excavation of the collapsingroundhouse. Two samples, 63 and 68, were collected from themain excavation trench across the diameter of the roundhousewhich truncated the central hearth. Sample 71 was collectedfrom context 46 in the doorway section in order to study theeffects of trampling and weathering (Table 1). Another samplewas collected from a working section from the wall edge inorder to study decay processes (Table 1) in an area wherebuilding materials had collapsed from the wall.

Fig. 3 Location of samples BLD1 and BLD3 on the section drawingthrough the Longbridge Deverill Cowdown roundhouse, Butser. Depositclassifications as follows: LD002 is a non-constructed earthen floor;

LD003 and LD004 are compacted trample deposits; LD005 andLD006 are in situ hearth ashes. Images A, B and C show the parallelorientation of plant material that is aligned parallel to the basal boundary



Tab

le2

Descriptio

nsof

deposittypes

andtheexperimentalsitesatwhich

they

wereidentified

Descriptio

nSite

Deposittype

Key

micromorphologicalfeatures

Interpretatio

nPrim

ary(P)/

secondary(S)/

tertiary

(T)

Butser

Lejre

St.Fagans

Pre-settlement

horizon

Sand

size

fractio

nisunsorted

andunoriented.T

hesilt-size

quartzfractio

nismoderatelysorted

andmoderately

unoriented.A

llotherinclusions

have

arandom

and

unreferred

distributio

n.

Sedim

entthatformed

before

thelocatio

nwas

used

asasettlem

ent/

experimentalsite.S

ortin

gandorientationof

inclusions

indicativ

eof

cultivatio

nin

thefieldbefore

constructio

n.Anearthw

orm

sorted

horizonthatwas

also

observed

inthesectionadjacent

totheearthw

orkatButser(Bell2

009).

PX

Sub-floor/hearth

levelling/

packing

>8cm

inthickness,hasamassive

beddingstructure,and

comprises

predom

inantly

rock

fragmentsandmineralwith

somesedimentaggregatesandplantrem

ains.U

nsorted.

Sedim

entthatw

asdepositedto

createalevelsurface.

SX

X

Non-constructed

earthenfloor

>9.5cm

inthickness.Loamysand,sandy

siltloam

orsilty

clay

loam

particlesize.M

idbrow

n(PPL),dark

brow

n(X

PL).

Embedded

relateddistributio

n.Occasionalsub-horizontal

fissures

inthemicrostructure.Anthropogenicdetritu

soccurs

atadepthof

9cm

.

Surfaces

createdfrom

theexistingground

surfacerather

than

afloor

createdby

there-deposition

ofsedimentfrom

elsewhere.T

hisfloor

creatio

nprocesshasbeen

previously

describedas

abeaten

earth

floor(M

acphailetal.2004).Tramplingandbioturbatio

nare

responsibleforanydownw

ardmovem

ento

fanthropogenicdebris.

Surfacemay

bemorereactiv

ethan

aconstructedearthenfloor.

PX

XX

Constructed

earthenfloors

Sandly

clay

loam

orsandyloam

particlesize.G

rey-mid

brow

n(PPL

),Grey-orange

brow

n(X

PL).Embedded

related

distributio

n.Anthropogenicdetritu

soccursin

theupper2cm

.

Using

eartheither

inits

unalteredform

orwith

additio

nalsandas

astabiliser,and/or

plantrem

ains

topreventcracking.Thismethodof

floorbuild

ingisfrequently

used

inearthbuild

ing(N

orton1997;

HoubenandGuillaud

1994;K

eefe

2005).

SX

Earthen

build

ing

material

Fabricused

asearthenbuild

ingmaterial,such

asdaub

orrender,

either

inits

unalteredform

orwith

additio

nalsandas

astabiliser,

and/or

plantrem

ains

topreventcracking.Thismethodof

floor

build

ingisfrequently

used

inearthbuild

ing(N

orton1997;H

ouben

andGuillaud

1994;K

eefe

2005).

SX

Com

pacted

tram

ple

Softmaterialsoriented

paralleltosurfaceof

theboundary

below.

Hardercomponentsareunoriented

andunrelated.

Deposition

of‘clods’of

dampsedimentw

hich

frequently

form

superimposedmicro-lam

inations

whendepositedwith

downw

ard

compression

onto

ahard

surface.

S,T

X

Discard

deposits

Unsorted.Inclusions

areunoriented,unrelated,random

and

unreferred.D

iverse

rangeof

componentsof

geological

source,and

high

frequenciesof

anthropogenicdebris.

Sedimentcontaininghigh

frequenciesof

anthropogenicmaterialsuch

assw

eepings.Re-depositedaw

ayfrom

theirprim

aryarea

ofdepositio

nby

anthropogenicprocesses.

SX

X

Accum

ulation

deposits

Non-organic,sandsize

inclusions

with

aparallelo

rientatio

nto

thebasalb

oundaryarecharacteristicof

theseaccumulation

deposits.S

ortin

gisoftenbimodal.

Accum

ulationcontextsfrom

theexperimentalsitescontainavery

specificrangeof

anthropogenicinclusions

reflectin

gtheactiv

ities

recorded

inthefield.

PX

XX

Rake-out

material

Unsorted.Inclusions

areunoriented,unrelated,random

and

unreferred.H

ighfrequenciesof

rubified

sedimentaggregates,

daub/furnace

lining,charredorganicremains,ash

andfresh

plantm

aterial.

Materialliesin

closeproxim

ityto

hearths.Rubifiedsediment

aggregates,daub/furnacelin

ing,charredorganicremains,ash

and

freshplantm

aterialh

avebeen

moved

from

theprim

aryplaceof

depositio

nwith

inthehearth

itself.

SX

Insitu

hearth

ashes

Lam

inated

beddingstructures

which

containmicrolenses

ofashes,charredplantrem

ains

andrubified

sedimentaggregates

which

areorientated

paralleltothebasalb

oundary.

These

asheshave

accumulated

insitu

andthereforelie

intheir

prim

aryplaceof

depositio

n.P

XX

Extensive

weathering:

very

abundant

evidence

ofmesofaunal

bioturbatio

n,(>20

%),occasionaldustyim

pure

clay

coatings

P,S,T

X



Laboratory methodology

Micromorphology samples were oven dried at 40 °C,impregnated with epoxy resin and cured. The impregnatedblocks were cut, mounted to slides and lapped to a standardgeological thickness of 30 μm. Micromorphologicalinvestigation was carried out using a Leica DMEP polarisingmicroscope at magnifications of ×40–×400 under planepolarised light (PPL), crossed polarised light (XPL) andoblique incident light (OIL). Thin section description wasconducted using the identification and quantification criteriaset out by Bullock et al. (1985) and Stoops (2003), withreference to Courty et al. (1989) for the related distributionand microstructure, Mackenzie and Adams (1994) andMackenzie and Guilford (1980) for rock and mineralidentification, and Fitzpatrick (1993) for further identificationof clay coatings. Tables of results use the descriptions,inclusions and interpretations format used by Matthews(2000) and Simpson (1998). Post-depositional alterationswere identified and quantified using a visual estimate(Bullock et al. 1985).

Deposit type classification

The depositional events are characterised by the followingdiagnostic sedimentary attributes: sorting, related distribution,orientation and distribution of the inclusions, and beddingstructure (for full deposit type descriptions see Banerjea2011). The range of deposit types that were identified fromexperimental sites are summarised in Table 2. To determinedeposit type, each unit was grouped using diagnosticsedimentary attributes and inclusions to provide informationconcerning the origin of inclusions, transportationmechanisms and deposition processes. To assess the originof sediment components, descriptions were made of particlesize, shape and the composition of the coarse and fine fraction,particularly the frequency of rock, minerals and anthropogenicinclusions.

Results and discussion

Following observation and description, deposits were groupedinto deposit types. Transportation mechanisms observed anddescribed include wind and water transportation, trampling,construction and accumulation. Deposition ‘hotspots’ wereidentified as well as post-depositional alterations. These arediscussed in detail below, and presented in Tables 3, 4 and 5.

Transportation processes of materials in experimental huts

Field observations identified the following routes and cyclesof transportation of materials within the experimental huts:T

able2

(contin

ued)

Descriptio

nSite

Deposittype

Key

micromorphologicalfeatures

Interpretatio

nPrim

ary(P)/

secondary(S)/

tertiary

(T)

Butser

Lejre

St.Fagans

Post-depositio

nal

soilform

ation/

'darkearth'

(2–5

%),rare

silty

clay

coatings

(<2%);rare

iron

translocation(<2%)andoccasionalvivianite

neom

ineral

form

ation(2–5

%).Po

st-depositionalprocessessuch

assurfaceearthw

orm

castsandvegetatio

ngrow

thandrounded

earthw

orm

granules,20%

werealso

evidentd

uring

excavatio

n.

Particlesof

rock,m

ineralandorganicdebris(dung)

thathave

been

reworkedandtransformed

bypost-depositionalbiological

processesto

form

asoil.

Mixed

compacted

tram

pleand

accumulation

Accum

ulationprocessesareevidentb

yboth

theorientationand

distributio

nof

sand-sizeinclusions

andlaminated

bedding

structures.S

ofterinclusions

such

asplantrem

ains

which

have

aparallelstrongorientationalignedwith

thebasalb

oundary

arecharacteristicof

depositio

nby

tram

pling.

Depositwhich

form

edby

bothtram

plingandaccumulationprocesses.

Thinlenses

with

strong

parallelo

rientatio

nanddistributio

nof

componentsgenerally

suggestp

eriodicaccumulationand

compactionover

time(G

oldbergandMacphail2

006).

S,T

XX

Mixed

dump

depositand

accumulation

Linkedandcoated

lenses

(1–2

mm

inthickness)interspersed

with

embedded

lenses.

Embeddingmay

have

occurred

whenpeoplestoodhere

toem

pty

sweepingsinto

theadjacent

basket.

P,S

X



wind and water/rain-induced transportation, trampling andtransportation by human agencies such as maintenance anddiscard processes. Results of observations of accumulationprocesses are given in Table 3. Results of observations oftrampled deposits are given in Table 4.

Wind and water or rain-induced transportation

In the external unroofed space outside the metalworkingworkshop at Butser, the accumulated deposit (context 003,sample B14) has a moderately sorted silt component whichmay have been transported by wind or rain. The bimodalsorting of poorly sorted/unsorted sand in this moderately sortedsilt, suggests that specific activities contributed to the input ofeach these components. Similar bimodal sorting characterisedinternal accumulated occupation deposits elsewhere at Butser,including in situ ashes, and at Lejre. The moderately sorted siltcomponent in deposits within internal spaces in the Forge atLejre, may have been left behind on the floor after sweepinghad removed larger sand-sized components (La Motta andSchiffer 1999; Metcalfe and Heath 1990), as percolated/’sieved’ sediments through mats (Matthews et al. 1997:289),or wind-blown sediments close to an entrance .

Trampling as a depositional pathway of materials

Compacted trampled deposits were identified in wet, open orpartially open, experimental buildings at Butser, in samplesBLD1 and BLD3, in an area where the roof had beenpartially removed (Fig. 3). They were also identified inmixed accumulation/trample deposits that occurred indoorways at Lejre in the sunken-shack (sample L45), andin the Moel-y-Gaer roundhouse St. Fagans (sample 71)(Fig. 6). Trampling acted as a depositional process(Table 2) transporting ‘clods’ of sediment from the soles offeet onto the floor surface. The parallel orientation of softmaterials such as plant remains suggests that downwardcompression aligned these malleable inclusions parallel withthe surface of the context below (Fig. 3). Harder materialssuch as rock fragments, minerals and metallurgical residues(Fig. 6a–c) are unoriented, randomly distributed and do notlie referred to any other components. The deposition of‘clods’ of sediment from the soles of feet formed lenses ofsediment when compressed during deposition oncomparatively dry surfaces in roofed spaces (Fig. 3 samplesBLD1 and BLD3, mixed trample/accumulation deposits insample L45, Lejre and sample 71, St. Fagans); trampling in

Fig. 4 The Iron Age Village, Lejre Historical and Archaeological Research Centre. A : Photograph of Building 2. B : Sketch plan of the interior ofBuilding 2. C : Photograph of the Forge. D : Sketch plan of the interior of the Forge



wet sediments can result in homogenous thick layers(Matthews 1995). Thin lenses with strong parallelorientation and distribution of components also generallysuggest periodic accumulation and compaction over time(Goldberg and Macphail 2006, p221).This superimpositionof lenses often results in the context having a laminatedbedding structure.

Compacted trample deposits can contain debris fromprimary and secondary, or even tertiary activities. At Butser,the same types of rock and minerals types in the compactedtrample deposits were also present in the external pre-settlement construction horizon and the internal non-constructed earthen floor, indicating that they could have beencollected on the soles of feet from either inside or outside, theLongbridge Deverill roundhouse. At St. Fagans, the mixedtrample/accumulation deposit in the doorway of the Moel-y-Gaer roundhouse contained metallurgical residues (metalfragments, <30 %, and slag, <15 %) that had most likely beentrampled into the building from a nearby metalworking area,or perhaps from the hearth area within the building where afew metalworking residues (<15 %) occurred in primarycontexts. Based on these observations, it is important

to consider that, when studying the use of space withinarchaeological buildings, artefacts and biologicalremains within doorways may not only reflect theactivities within the building, but also those activitiesthat are taking place in open spaces and adjacent areasaround buildings.

In order for compacted trample deposits to form, thisresearch has demonstrated that damp environmentalconditions must be present. Damp conditions are crucial forthe formation of compacted trampled deposits or deposits thatcontain a proportion of material which has been deposited bytrampling. Damp conditions are evident by the concentrationsof eroded building materials from the walls, clay coatings andchemical alterations such as neomineral formations (Table 4).Building collapse, or the partial removal of roofs, also playedan integral role in the formation of internal deposits ofcompacted trample, by contributing higher densities ofsediment and mud materials to locales, which were laterfrequented and trampled. A mixed trample/accumulationdeposit developed within the Sunken Shack, Lejre, after theroof has failed (Fig. 5). At Butser, compacted trample deposits(contexts LD003 and LD004) had formed within the

Fig. 5 Location of micromorphology samples collected within the sunken-shack, Viking Village, Lejre Historical and Archaeological Research Centre,Lejre: L45 from side A , the roofed space; L51 from side B , the unroofed space



Longbridge Deverill roundhouse during a period ofbuilding collapse when the interior of the buildingbecame wet in the month or so before sampling, butthe area was still visited.

Chemical weathering has also been observed in compactedtrample deposits from experimental buildings (Table 4). Theidentification of compacted trampled deposits has thepotential to be a useful indicator of doorways or pathways inthe archaeological record, particularly where there is littleremaining archaeological evidence for the superstructure ofthe building.

Transportation by human agency: inclusions within floorconstruction materials

Earth materials were used in the construction of levelling andfloor surfaces (Table 2) within the experimental buildings, andinclusions within floor surfaces can either be primary orsecondary depositions. Deposits classified here as non-constructed earthen floors (Table 2) refer to surfaces on theoriginal ground surface, often including trampling ofvegetation (Macphail et al. 2004), which therefore can beconsidered as a primary constituent of a floor surface.

Fig. 6 Location of micromorphology sample 71 on the section through the doorway of the Moel-y-Gaer roundhouse, St. Fagans (top left). Images A-Eare microscopic residues from metalworking activities within the mixed trample/accumulation deposit in the doorway, of the roundhouse

Table 3 Sediment attributes of experimental archaeology deposits that have formed by accumulation processes

Deposit typenumber

Samplenumber

Contextnumber

Building Location inbuilding

Particle size Sorting Inclusions: Orientation and Distribution

Accumulation L39 013 Forge Close tohearth

Silt loam Bimodal: mod sortedsilt in poorly sortedsand

Larger sand sized particles (>250 μm) areunorientated and unreferred. Others arehave a linear and parallel distributionand are moderately orientated.

B14 003 Metalworkingshed

Open porcharea

Sandy clayloam

Bimodal: Unsorted sandsize, moderatleysorted silt.

Mostly Unorientated and unrealted.Random and unreferred. Sand-sizedinclusions have a linear and inclineddistribution and moderately orientated.

In situ Ashes BLD1 LD005 LongbridgeDeverillCowdownR/H

Hearth Coarse sandyclay loam

Bimodal: Unsorted sandsize, moderatleyorted silt.

Unorientated and unrealted. Random andunreferred. But most charcoal and plantfragments have a linear and inclineddistribution and moderately orientated.



Specific examples of this observed at the experimental sitesinclude: the Longbridge Deverill Cowdown roundhouse,Butser, context BLD002 (Fig. 3); the disused forge, Lejre,(Fig. 4) context L014; and the Moel-y-Gaer roundhouse St.Fagans (Fig. 6), sample 68). Sub-floor levelling material andconstructed earthen floors (Table 2) comprise sediment thathas been transported from elsewhere and deliberatelymodified with aggregate to increase the strength of thematerial, or vegetable stabilisers to prevent cracking (Norton1997; Matthews 1995; van der Veen 2007), as observed inBuilding 2, Lejre. In this case, these inclusions can beconsidered to be in a secondary context in floor materials.

Primary and secondary materials in floor surfaces,therefore, were transported through very different depositionalprocesses. Coarse sand aggregates increase the strength of anearthen building material (Berge 2000). This is evident at Lejrewhere sub-floor levelling deposits and constructed earthenfloors within Building 2 were made from glacial till, quarriedfrom a clay pit adjacent to Building 2. These floor surfaces arehard and compact. The glacial till floors included coarse flintrock components and minerals such as quartz. At Lejre, it wasused in sub-floor levelling material (context 002, sample L1)and the original constructed earthen floor (context 005, sampleL9) in Building 2 (Fig. 7), and is broadly similar to the non-constructed earthen floor (sample L39), in the Forge, Lejre(Fig. 8), but with a greater frequency of flint inclusions,feldspars, amphiboles and chlorite minerals in Building 2(Fig. 7) than the non-constructed floor (context 014) in theforge (Fig. 8). Context 020, Building 2, Lejre, has a differentrock and mineral composition than the original constructedearthen floor (context 005), specifically the inclusion of chalkfragments (Fig. 7), which reflects the use of a different sourcematerial used to repair the floor. This ‘chalky clay’ wascollected from a source some distance away (Hans OlHansen personal communication).

It is not known whether higher frequencies of flintfeldspars, amphiboles and chlorite minerals in the sub-floorlevelling and original constructed earthen floor materialsBuilding 2 relate to the addition of aggregate duringpreparation of the sub-floor levelling material and constructedearthen floors, or whether the variability reflects theexploitation of different seams of glacial till source material.As observed in the construction of modern brick making, thenature of the quarrying method can influence the nature of thesource material. This depends on whether a uniform sedimentseam was selected, or whether downwards excavationquarried and mixed different sediment seams (Prentice 1990).

Transportation by human agency through accumulationprocesses

Accumulation contexts from the experimental sites contain avery specific range of anthropogenic inclusions reflecting theT

able4

Weatheringwith

inexperimental(Butser,Lejre

andSt.F

agans)compacted

tram

pledepositsandmixed

tram

ple/accumulationdeposits

Siteandsampleinform

ation

Translocatio

nChemicalalteratio

nDecay

Deposittype

Sample

number

Context

number

Building/site

Dusty

impure

clay

coatings:

unlaminated

Dusty

impure

clay

coatings:

microlaminated

Iron

Vivianiteneom

ineral

form

ation

Manganese

neom

ineral

form

ation

Organic

staining

Spherical

fungalspores

Com

pacted

Trample

BLD1

LD004

LBDR/H,B

utser

ab

c

BLD3

LD003

LBDR/H,B

utser

cc

c

Mixed

tram

ple/

accumulation

L45

016

Sunken-shack,L

ejre

bd

b

SF71

46R/H,S

t.Fagans

cc

d

aOccasional2

–5%

bRare<2%

cMany5–10

%dAbundant1

0–20

%



activities recorded in the field. Accumulations have bimodalsorting, poorly/unsorted sand in moderately sorted silt, anembedded and coated related distribution, and the inclusionsare moderately oriented and linear and parallel/inclined indistribution (Table 3). In comparison, discard deposits are

unsorted, often have an intergrain aggregate and/or linkedand coated related distribution, and inclusions are unorientedand randomly distributed, indicating higher energy in thedeposition (Table 2); they also contain a greater diversityand frequency of inclusions than accumulation deposits.

Table 5 Differences between the sediment properties (field descriptions) in the roofed and unroofed sides of the Sunken Shack, Lejre

Sediment attribute Context (016) roofed Context (017) unroofed

Thickness 1–5 cm 4–10 cm

Bedding Layered (lenses of dung) Massive

Colour Brown black Very dark brown

Consistency and structure Strong. Platey (coarse material) and blocky (fine) structure.Non-plastic and non-sticky.

Very weak. Crumb (fine–med) structure.Slightly plastic and slightly sticky.

Particle size Sand Sandy clay

Post-depositional alteration Trampling. Wind and rain bringing in leaves and acorns. Trampling. Root activity. Soil development.Surface worm casts. Wind and rain.

Inclusions: orientation/distribution Parallel and random Unoriented and random

Inclusions: composition, shape,size and abundance

Dung (SR) <2 cm, 60 % Dung (R) <1 cm, 10 %

Straw (A) <10 cm, 5–10 % Charcoal (A) 1–2 cm, 5 %

Flint (A) <5 cm, 5 % Bone (A) 2–5 cm, 10 %

Fur (R) 2–4 cm, <5 % Acorns (R) 2–3 cm, 5 %

Acorns (R) 2–3 cm, 5 % Leaves (R) 5–7 cm, 5 %

Leaves (R) 5–7 cm, 5 % Earthworm granules (R) 0.4 cm, 20 %

Fig. 7 Spatial distributions of rock and mineral inclusions within constructed earthen floors and sub-floor levelling material in Building 2, Lejre



Compacted trample deposits also show linear and paralleldistribution and local orientation of plant fragments(Table 2), whereas in accumulations, the linear and paralleldistribution and local orientation occurs in the coarser hardermaterials (Table 3).

Periodic, accumulation processes often result in the build-up of primary activity residues, attested in thin section(Table 3) by parallel orientation of coarse components alignedwith the basal boundary (Goldberg and Macphail 2006).Examples of this from these experimental sites include: pelletsof herbivore dung (context 016) in the Sunken Shack, Lejre;daub in Building 2, Lejre (context 004); and metalworkingresidues and charcoal within the accumulation context (003)outside the Metalworking shed, Butser. Micro-laminations,such as superimposed fine lenses of calcitic ash that formedin in situ hearth ashes (Fig. 3, sample BLD1 context LD006)within the central hearth, Longbridge Deverill roundhouse,Butser) often also indicate repeated, periodic accumulations

(Goldberg and Macphail 2006). Within in situ hearth ashes,such as context LD006 Butser, charcoal and plant remainswere observed to be moderately oriented, with a linear andinclined distribution, often lying referred to larger charcoalfragments which they have fallen against during deposition(Table 3).

Identifying interior ‘hot spots’ of deposition

Composition and Spatial Distribution of Discard Deposits

Micromorphological observations from Building 2, Lejre(Fig. 9), demonstrate that the discard deposits in interiorspaces may comprise materials that were transported andincorporated from around the entire building, as well as higherfrequencies of a particular material where the catchment forthe dump is close to a specific activity area.Within Building 2,discard deposits 006, 021 and mixed discard/accumulation

Fig. 8 Rock and mineral inclusions within the non-constructed earthen floor (context 014) and the overlying accumulation deposit (context 013) in theForge, Lejre



004 formed within depressions in the floor surface caused bythe moving of upright roof support posts which are locatedclose to the wall edge and external doorways in the living area.Fragments of daub and lime plaster building materialsoccurred in these dump deposits but not in the dump depositthat had formed within an axial dung channel in the formerstable area (context 001) within Building 2 (Fig. 9). Theoccurrence of building materials in these locations may bedue to the erosion by wind and rain, and abrasion by passingtraffic, of daub and plaster from the walls in the area of thedoorways that have then been trapped in the depressionsduring sweeping. Within the Moel-y-Gaer roundhouse at St.Fagans, the micromorphology observations of depositsadjacent to the edge of the wall showed that fragments oferoded lime plaster had accumulated in order of erosion fromthe wall face (Fig. 10). The earthen floor deposit below lens bcontained unlaminated and laminated silty clay and claycoatings (2–5 %). Microlaminated clay/silty clay coatingsexhibiting regular lamination and high birefringenceindicate strong parallel orientation of fine particles as aresult of slow aqueous deposition under calm conditions(Courty et al. 1989). It is possible that the alignment ofclay and silt particles in this area is due to damp/periodicpuddles, which may also have caused the erosion ofplaster and daub from the wall.

Higher frequencies of specific materials from localisedactivities within Building 2, Lejre, are present in dumpdeposits 001 and 006, proximate to the foci of these activities.In Building 2, context 001 contains dung representing theformer use of the stable area (Fig. 11) and context 006contains higher frequencies of fresh plant material as aresult of the incorporation of sweepings from thegrinding stone (Fig. 11).

Post-depositional alterations to hut floor deposits

The creation of new deposit types through post-depositionalprocesses

Micromorphology has demonstrated that post-depositionalprocesses can create new re-deposited lenses through clearexamples, firstly within the Moel-y-Gaer roundhouse, St.Fagans, and secondly within the sunken-shack, Lejre. In theMoel-y-Gaer roundhouse, micromorphological analysisshows that lens D (Fig. 10) was formed by the infilling of amesofaunal channel with material from lens B and so thisaccumulated material is a secondary constituent. Ant andhornet activity were both observed within the Moel-y-Gaerroundhouse during excavation. The activity and effects of antson the soil and archaeological deposits are less well

Fig. 9 Spatial distributions of building materials, artefacts and bone within occupation deposits in Building 2, Lejre



Fig. 10 Micromorphology features within deposits by the edge of wall,Moel-y-Gaer roundhouse, St. Fagans. The sample was collected from the slotmarked on the right of the excavation photograph (top left). This samplecomprises lenses a-e. Lenses a, b and d are accumulation deposits, lens c is

earthen building material, and lens e is a non-constructed earthen floor. A:Lens b, fresh plant material embedded within a plaster fragment (XPL). B:Lens e, finer quartz particle size and less rubified claymatrix than lens b (XPL).C: Lens c, coarse quartz particle size and more rubified than lens d (XPL)

Fig. 11 Spatial distribution of plant remains within occupation deposits in Building 2, Lejre



understood than for earthworms or termites, for exampleBrady and Weil (2002). In thin section, there are clear tracesof mesofaunal activity, most probably from ant activity and isrepresented by horizontal burrows that truncate the earthenbuilding material (Fig. 10, lens C). Material from lens B hasfallen through into a horizontal channel that the ants createdbetween the earthen building material (lens C) and the non-constructed earthen floor (lens E) forming lens D (Fig. 10).

Failing roofs can lead to post-depositional alterations thatradically transform the deposits within the building. Thesunken-shack, Lejre, was first used to demonstrate bone-working craft techniques to school children, before a changein use when it was used to house goats. A subsequent decisionwas taken by staff at Lejre to use the sunken-shack as a shelterfor sheep instead of goats, as the goats had destroyed the roofon one side, opening it up to the effects of weathering.Substantial post-depositional alterations had occurred within2.5 years in the unroofed half of the building leading to soilformation. This sequence of use and post-depositionalalterations is clearly attested in the microstratigraphic sequence.The differences between the roofed and unroofed side of thebuilding were clearly visible in the field and from the initialfield descriptions (Fig. 12; Table 5). Although the depositacross the floor of the sunken-shack had initially been the samestable floor deposit on both the roofed and unroofed sides of thebuilding, micromorphology revealed the extent to which the

unroofed side of the building had been radically transformed byexposure to weathering (Fig. 12), including for example,dissolution of faecal spherulites, probably by increased acidicconditions, below pH 7.7 when spherulites dissolve (Canti1999), and there is less fresh plant material in 017 than 016and phytoliths are present probably due to accelerated decayprocesses in the unroofed side of the building.

Abrasion processes on floor surfaces within buildings

Sweeping and trampling are major mechanisms in abrasion,disaggregation and transportation of floor materials andaccumulated deposits. They are most probably thetransportation mechanisms for some of the rock and mineralinclusions within discard deposits 006 and 021 from Building2, Lejre. The fragments of granite most probably derive fromabrasion through use of the adjacent granite quern stone andwere subsequently redeposited in the process of sweeping,and/or may also originate from erosion of the granite cobblesin the doorway (Fig. 7). By comparing rock and mineralcomposition of constructed earthen floors and sub-floorlevelling material in Building 2 (Fig. 7) with the compositionof the overlying dump and accumulation deposits (Fig. 13) itis possible to infer that certain rock and minerals in dumpdeposits did not occur in the directly underlying constructedearthen floors, but were eroded from elsewhere in the building

Fig. 12 Comparative sediment features from the roofed and unroofedspaces within the sunken-shack, Lejre. Note the linear and parallellaminations of the dung lenses in sample L45 compared to the unoriented

particles of dung in sample L51. Image A shows calcareous faecalspherulites that were not present in sample L51. Images B and C showbone fragments that did not occur in sample L45



and transported by sweeping processes. For example, chalkfragments occur in dump deposit 004 in Building 2 (Fig. 13),but not in the underlying constructed earthen floor 005(Fig. 7). However, chalk fragments do occur within arepaired patch of constructed earthen floor material, context020, on the other side of Building 2 (Fig. 7). Granite does notoccur in sub-floor levelling context 002 but does occur inoverlying dump context 001 and elsewhere in Building 2.This suggests that granite fragments may have beentransported by feet trampling across the granite cobbles andthe area adjacent to the granite quern stone, and through thestable area rather than from incorporation due to the erosionof the underlying floor (Figs. 7 and 13). By comparing rockand mineral assemblages in floor materials and their overlyingoccupation deposits, sequences of activity and repair may beidentified.

The erosion of building materials

The categories of building materials identified withinsecondary occupation deposits from Building 2 (Fig. 9) andprimary occupation deposits in the Sunken Shack at Lejre(Fig. 14) in thin section correspond with those recorded inthe field in the construction materials of the buildings.

Micromorphological analysis suggests that their distributionis quite localised within the buildings. The original bitumenroofing had become weathered and fragmented andincorporated into 017 within the now unroofed side of theSunken Shack, Lejre. Fragments of daub in occupationdeposit 004 and daub and plaster within 006 and 021,Building 2 Lejre within 1 m of the wall. In thin section, theparallel orientation of the fragments to the basal boundary on004, suggest that it was eroded daub from the walls. Bycomparison, the haphazard unoriented distribution offragments of building materials in dumps 006 and 021 suggestthat these were redeposited by sweeping.

Weathering processes and trampling appear to haveeroded granite floor cobbles in the Sunken Shack, Lejre,as micro-fragments of the cobbles became incorporated,most probably through bioturbation, into the overlyingoccupation deposits (Fig. 15) which had formerly been amixed compacted trample/accumulation deposit (as on theroofed side of the building) but now post-depositional soilformation on the unroofed side of the building.Bioturbation (eg mixing by fauna) also introduced unburntbone fragments which had been deposited during previouscraft activities into post-depositional soil formation deposit(context 017) (Fig. 14).

Fig. 13 Spatial distribution of rock and mineral inclusions in occupation deposits within Building 2, Lejre



Localised chemical alterations within occupation deposits

Experimental research has provided crucial observationsconcerning the effects of fluctuations in the oxidised/reducing conditions within non-waterlogged occupationdeposits from temperate sites (Fig. 16). Within occupationdeposits inside buildings, chemical alterations can play a keyrole in the formation of silty clay coatings, in addition toturbulent hydraulic conditions and mixing and rotating offloor deposits inducing clay and silt translocation at temperatesites (Courty et al. 1989; Goldberg and Macphail 2006).

Chemical alterations and changes in the redox (oxidationreduction processes) conditions can lead to the dispersal of siltand clay particles (Brammer 1971; French 2003) within highlylocalised areas, often in lenses or patches with decayingorganics, in occupation deposits within roofed spaces. AtLejre, moderately or strongly oriented silty clay coatings indump deposit 021 and mixed dump/accumulation deposit 004are associated with areas of organic decay and staining(Fig. 16c and f). As this spaced is roofed and not open to theeffects of wind and rain, it is possible that chemical changescaused by the decay of organic matter, and turbulent conditions

Fig. 14 Comparative figure showing the frequency of building materials and artefacts before (context 016) and after (context 017) weathering in thesunken-shack, Lejre



from dumping processes and trampling, are causing themobilisation of silty clay particles, rather than rainwaterflowing though the profile. Within this context, stronglyoriented clay coatings of voids and minerals formed in linearand parallel lenses occur horizontally across deposit 021 inclusters associated with areas of plant decay and thebreakdown of daub. These areas of clay coatings are a differentcolour (orange PPL, dark orangey with occasional dark yellowXPL) from the surrounding matrix (dark brownish grey PPL,very dark greyish brown with hints of very dark brownish red

XPL). Iron and manganese appear to have replaced organicmaterial within the deposits LD005, Butser (Fig. 16a and d)and L021, Lejre (Fig. 16c and f) and there is also organicstaining in context 001 (Fig. 16b) and context 021 (Fig. 16e)and similarly, also in deposit 004. The silty clay coatings mayhave been impregnated with iron. Iron and manganese replacethe organic matter. At Buster, ashes within the hearth that hadbeen left open to the effects of rain, have also begun to bereplaced by manganese (Fig. 16a). Here, the silty clay coatingsare impregnated with iron, and clay coatings within a decaying

Fig. 15 Comparative figure showing the frequency of rock fragments and minerals before (context 016) and after (context 017) weathering in thesunken-shack, Lejre



piece of wood have internal iron mottles. Within the in situhearth ashes at Butser contexts LD005 and LD006, moderatelyoriented silty clay coatings are sometimes mixed with ash andare different in colour from surrounding ash matrix, suggestingthat it has been incorporated from another source. They are asimilar colour to material in overlaying trample depositLD004, and may also be impregnated with organic staining.These characteristics resemble those from other studies, inwhich clay coatings which have a different colour from thesurrounding sediment matrix are suggested to have beentranslocated from elsewhere and washed into the sedimentprofile (Brammer 1971; French 2003). Where clay coatingsare the same colour as the surrounding matrix, as observed insome seasonally flooded sediments, Brammer (1971) andFrench (2003) have suggested that seasonal alterations ofreduction and oxidation of topsoils may lead to the dispersalof fine material during the period when the iron present isstrongly reduced thus, as suggested by French (2003), causingclay coatings to become impregnated with iron oxides andhydroxides. Where animal penning has taken place, animaltrampling and inputs into the soil of organic matter-rich dungand liquid waste mobilises fulvic acid to produce dark reddishbrown clay coatings (Macphail and Linderholm 2004;Macphail and Cruise 2001).

It is apparent at both Butser and Lejre that chemical changesrelated to the decay of organic matter and dung and itsreplacement with iron andmanganese (Fig. 16), in conjunction

with anthropogenic and livestock disturbance, is causing finesilts and clays within the deposits to disperse. However, furtherresearch monitoring redox potential over time in non-waterlogged occupation sediments in both roofed andunroofed contexts is required to understand these processesfurther. The timescales for these chemical changes at Butserand Lejre suggest that these processes can take place withinmonths after deposition. These processes are more prolific atLejre. The more alkaline calcareous environment at Butser, inconjunction with earthworm activity, may prevent localisedchemical changes (Crowther et al. 1996), which require moreacidic anaerobic conditions, from taking place to the extentwhich can be seen at Lejre, although manganese replacementof calcitic hearth ashes does occur (Fig. 16a).

Conclusions

Examination of field and micromorphological characteristicsof architectural materials, surfaces and deposits at theseexperimental sites has produced significant observations thathave further developed identifications of formation processesin the archaeological record, particularly the identification oftrampling, the radical transformations that take place as aresult of post-depositional events both in roofed and in poorlyroofed spaces, and the timescales over which processesoccur.

Fig. 16 Micromorphological features resulting from localised redoxprocesses on experimental sites: manganese replacement of ashes, PPL(A) and XPL (D), sample BLD1, context LD005, Butser; image B ,decaying plant material with organic staining (top left ), manganesereplaced plant remains (top centre), iron mottles (bottom), PPL, sample

L1, context L001, Lejre; band of silty clay translocation directly belowmanganese replacement of decaying plant remains, PPL (D) and XPL(F). Sample L15, context L021, Lejre; image E , manganese replacementof decaying plant remains, PPL, sample L15, context L021, Lejre



The parallel orientation of soft materials such as plantremains suggests that downward compression aligned thesemalleable inclusions parallel with the surface of the contextbelow. Harder materials such as rock fragments, minerals andmetallurgical residues are unoriented, randomly distributedand do not lie referred to any other components. Thedeposition of ‘clods’ of sediment from the soles of feet formedlenses of sediment when compressed during deposition oncomparatively dry surfaces in roofed spaces.

Post-depositional processes have been shown to have theability to transform stratigraphy to create entirely new deposit-types. At St. Fagans, ant activity created a new layer belowthose that had been previously deposited. At Lejre, it has beendetermined that failing, leaking roofs can radically transformoccupation deposits within buildings and eventually lead tosoil development, which may resemble a ‘dark earth’(Macphail and Courty 1984; Macphail et al. 2000; Macphailet al. 2003), including anthropogenic debris from the period ofbuilding use. This could have significant implications for theidentification of structures in the archaeological record,particularly when superstructure components such as wallsand beam slots are not visible, and these deposits may bemisinterpreted as garden soils in external areas.

Localised redox processes can play an important role in themobilisation of silts and clays as a result of weathering anddecay processes within occupation deposits. However, it mustbe noted that these processes are difficult to relate to specificstages in the life of archaeological structures. Thisexperimental analysis has shown that chemical alterationscan occur within months of deposition. Experimental researchhas also demonstrated that geology will play an integral role inthe formation of localised redox processes in occupationdeposits. Additional influences are the types of sourcematerials for building and the function of the area in termsof the inputs of residues.

Certain locations within buildings have been identifiedwherespecific deposit types have both formed, and are more likely tosurvive. The occurrence of compacted trample deposits may beused to identify damper areas of buildings such as doorways orsemi-open spaces in the archaeological record. The study of thespatial distribution of discard deposits within experimentalbuildings has demonstrated that their formation and survival isdependent on the occurrence of catchments that were formed bythe modification of super-structural components causingdepressions in the floor, and that the protection of residues byinternal furniture leaves areas that escape sweeping such as thejunction of the base of the wall and the edge of the floor.

Building reconstructions at experimental sites can act as‘working laboratories’ for archaeologists to study the formationof the archaeological record and life histories of buildings,provided basic constructional and activity information isregularly recorded. However, experimental sites are notethnoarchaeological case studies as the buildings have often

been utilised to different extents. The experimental sites atButser, Lejre and St. Fagans have provided opportunities tospatially examine specific activity areas and formationprocesses within medium term experimental archaeologybuildings. Spatial analysis within experimental buildings hashighlighted the importance for archaeologists to devisesampling strategies for use in archaeological buildings withconsideration to the possible layout of internal furniture,depressions in floors and in areas of structural modification,as these factors effect residue accumulation.

Acknowledgements The authors would like to acknowledge the Artsand Humanities Research Council for funding Rowena Banerjea’sdoctoral research, Lejre Historical and Archaeological Research Centrefor a small research grant, the School of Human and EnvironmentalSciences, University of Reading, for funding the ‘Life-Histories ofBuildings and Site Formation Processes’ research project, which formedpart of this research, and the National Museum of Wales for funding theexcavation and sampling of theMoel-y-Gaer roundhouse at St. Fagans. Inaddition, the authors would like to thank the staff at Butser, Lejre and St.Fagans, and all fieldwork team members for their assistance andcontributions. Particular thanks go to Christine Shaw (Butser), MarianneRasmussen (Lejre), Ken Brassil, Dr Adam Gwilt and Ian Daniels (St.Fagans), Nina Helt-Nielsen (University of Aarhus) and the following atthe University of Reading: Professor Michael Fulford, Dr Rob Hosfield,Professor Stephen Nortcliff, Dr Jennifer Foster, Amy Poole andChristopher Speed.

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